The present invention relates to improved process for producing ivorylike material for keys of musical instruments, and more particularly relates to improvement in production of artificial material for musical instruments having appearance and properties very close to those of natural ivory.
Ivory has long been highly appreciated by ones skilled in the art of keyboard musical instruments such as pianos, organs and accordians as a material for composing at least surface parts of keys. Such a lean towards ivory is believed to be caused by, aside from the fact that ivory is mainly used for high class art objects, its ideal properties which well suffice all of the following complicated requirements for the material to be used for keys of musical instruments of the above-described sort.
(a) The material should have moderate moisture absorbability so that a key should well absorb sweat on the fingers of players in order to prevent undesirable finger slippage on the key during performance. PA1 (b) The material should have moderate surface smoothness with moderate frictional resistance since these factors have subtle influences on key touch. PA1 (c) The material should have excellent appearance, i.e. high whiteness accompanied with high contamination resistance. PA1 (d) The material should have moderate hardness which assures better key touch and less frictional abrasion over a long period. PA1 (e) The material should have moderate workability for easy shaping into keys.
Despite such ideal properties, use of ivory for keys has a serious disadvantage of poor supply which falls short of increasing demand in production of keyboard musical instruments.
As a substitute, use of synthetic resins have been increasingly employed for years in production of keys for musical instruments since they are suited for mass-production which assures constant and sufficient supply. Synthetic resin keys, however, still have several drawbacks despite their relatively beautiful appearance and flexible workability. First, excessive smooothness of synthetic resins often causes undesirable finger slippage on keys during performance. This trouble is further amplified by poor moisture absorbability of synthetic resins which disenalbes effective absorption of sweat on fingers. Further, synthetic resins in general have relatively low hardness which may allow quick frictional abrasion of keys.
In an attempt to avoid the above-described drawbacks of synthetic resins when used for keys of musical instruments, the inventor of the present invention already proposed a new process in U.S. patent application Ser. No. 501,968 now U.S. Pat. No. 4,447,268 (a continuation of the parent application Ser. No. 296,483 filed in 1981 now abandoned). In the case of this proposed method, either hydrated or non-hydrated inorganic filler is used in combination with casein. More specifically, casein is mixed and kneaded with filler and water and, after shaping the mixture into a block, the block is impregnated with formalin for hardening. This proposed process well develops high moisture absorbability and good affinity to human skin of casein plastics, a natural protein. Further addition of the inorganic filler greatly improves hardness, thermal conductivity and massive impression of the product, which is believed to have by far exellent properties than the conventional keys made of synthetic resins.
When compared with keys made of natural ivory, however, keys made of the casein plastics are still inferior in appearance and cannot avoid to give a different impression. This is due to the fact that mere mixing and kneading of casein with filler cannot develop deep and flowing stripes on the surface of the product which are special to natural ivory.
It is also proposed to develop varicoloured patterns on the surface of a product by extruding a mixture of caseins of different colours on a multi-cylinder type extruder. This process, however, is again unable to develop subtle, flowing stripes on the surface of the product which are in general possessed by natural ivory.